1. Field of the Invention
This invention relates to an improved phosphorescent textile fiber and to a process for producing such phosphorescent fiber suitable for use in the production of textile articles.
2. Description of the Prior Art
Synthetic resins or polymeric materials having phosphorescent or luminescent qualities have been used to make a wide variety of goods such as amusement devices, signs, safety devices, articles of clothing and the like. It is also known to use fluorescent dyes in the production of commercial textile articles including yarns and the like. It should be pointed out, however, that the arts of producing phosphorescent and fluorescent materials are quite different in many instances. For example, many fluorescent dyes of are relatively lightweight compounds whereas phosphorescent materials such as zinc sulfide may be relatively heavy in comparison with the synthetic resin materials to be treated.
U.S. Pat. No. 2,382,355 to Warren discloses a luminous rope in which the filaments are formed from a resinous material having a suitable luminous material molded within the filaments. According to the patent, the phosphorescent (or fluorescent) material is mixed in the plastic while in the powdery form or at any point in the rope making process prior to the extrusion or cold rolling of the plastic into filaments so that the luminous material is dispersed throughout the mass of plastic. In other embodiments, the luminous material is mixed in a plastic carrier and coated on the filaments, then covered with a transparent or translucent plastic coating. The individual filaments are formed by stretching or drawing through a die to orient the molecules in the strand for tensile strength.
U.S. Pat. No. 2,436,182 to Schmidling discloses a molded phosphorescent device formed from a resin material having a phosphorescent filler blended throughout the resin. Various articles are made from the relatively heavy rigid molded mass.
U.S. Pat. No. 2,838,762 to Wadely discloses a floor covering or rug having designs therein formed from yarns which are impregnated with a phosphorescent material. The phosphorescent yarns are coated with a binder which permits the transmission of light therethrough.
U.S. Pat. No. 4,640,797 to Goguen discloses a process for preparing a phosphorescent polymeric material for use in the molding of shoes for runners, cyclists, or the like, and in which the elastomeric material and from 20 to 50% by weight of processing oil is heated and blended in an extrusion apparatus and then from 3 to 30% by weight of a phosphorescent material (with other ingredients) is blended with the melting ingredients as thoroughly as possible before the finished product is formed into pellets or the like for subsequent use in molding the shoe soles. The oil used is as a plasticizer for the polymeric material.
U.S. Pat. No. 4,781,647 to Doane teaches a process for extruding a thermoplastic polymer containing a mixture of phosphorescent particles. The extrusions are of a dimension to be suitable for use to make doll hair which glows in the dark. The phosphorescent material is stated to have a maximum particle size which is less than one half the diameter of the strands. The strands have a diameter of less than 0.015 inches and preferably in the range of 0.002 to 0.004 inches, and preferably the polymeric material consists of polyamides, polyesters, polyolefins, polyacrylonitriles and polyvinyl chlorides. The phosphorescent material may be zinc sulfide, cadmium sulfide or calcium sulfide. A coupling agent is used to coat the phosphorescent particles to enhance mixing.
U.S. Pat. No. 5,135,591 to Vockel et al discloses a process for making phosphorescent fiber reinforced plastic articles in which the a phosphorescent material is encapsulated on a surface of the molded finished product.
While it is apparent from the above and other prior art patents that extensive efforts have been made to utilize the phosphorescent properties of materials such as zinc sulfide, substantial difficulty has been encountered in producing satisfactory products. For example, it is not heretofore been considered practical to form a phosphorescent fiber suitable for use in yarn such as bulked continuous filament (BCF) yarn of thermoplastic polymers such as polypropylene, nylon, and polyester having properties suitable for commercial use in the textile industry. For such use, it is obvious that the yarn must possess and retain a high degree of uniformity in the phosphorescent properties as well as color and the like, and that the phosphorescent materials used not adversely affect processing characteristics, including dyeing or physical properties of the yarn or filaments formed.
While it cannot be determined for certain, it is believed that a primary problem in producing synthetic yarns having phosphorescent particles therein has been the inability to adequately mix the phosphorescent material with the synthetic resin material. The relatively heavy nature of the most widely used commercial phosphorescent material, when compared with the weight of the polymers used, tends to cause the phosphorescent material to settle. Further, in the past the dry phosphorescent material has generally been added in the melt extruder where the auger was relied upon to physically agitate and mix the materials. It is apparent, however, that for forming of very fine fibers or filaments, only slight variations in the concentration of solid particles can result in inferior product or even interruption of the process.
In the production of BCF yarn of thermoplastic polymers in a commercial melt spinning line, pigment or other foreign matter loading above about 1% for solution dyed yarns are generally considered unusual and loadings of 2 to 3% have been considered to be the upper limit for such commercial manufacturing process.
It is an object of the present invention to provide an improved method of producing continuous phosphorescent filaments or fibers suitable for use in the textile industry.
It is another object of the present invention to provide an improved method of melt spinning phosphorescent yarns or filaments from a thermoplastic polymer material.
Another object is to provide such a method which enables loading of the polymer material with a relatively high percentage of finely divided phosphorescent pigment to produce a high degree of phosphorescence.
Another object is to provide an improved monofilament, spun, continuous filament and/or BCF phosphorescent yarn which has a substantially uniform phosphorescent property.
Another object is to provide an improved textile fiber or filament produced by such a process.